1. Field of the Disclosure
Exemplary embodiments of the present disclosure relate to an image forming apparatus, such as a copier, a printer, a facsimile machine, or a multi functional device having at least two of the foregoing capabilities, and a fixing device employed in the image forming apparatus.
2. Description of the Background Art
Image forming apparatuses, such as copiers, facsimile machines, printers, or multifunction apparatuses having at least two of copying, printing, scanning, and facsimile capabilities, typically form an image on a recording medium according to image data. In such an image forming apparatus, for example, a charger uniformly charges a surface of an image carrier; an optical writer emits a light beam onto the charged surface of the image carrier to form an electrostatic latent image on the image carrier according to the image data; a development device supplies toner to the electrostatic latent image formed on the image carrier to make the electrostatic latent image visible as a toner image; the toner image is directly transferred from the image carrier onto a recording medium or is indirectly transferred from the image carrier onto a recording medium via an intermediate transfer member; a cleaner then cleans the surface of the image carrier after the toner image is transferred from the image carrier onto the recording medium; finally, a fixing device applies heat and pressure to the recording medium bearing the toner image to fix the toner image on the recording medium, thus forming the image on the recording medium.
Such a fixing device may include a substantially cylindrical metal member to effectively heat an endless fixing belt serving as a fixing member to shorten a warm-up time or a time to first print (hereinafter also “first print time”). Specifically, the metal member, which is heated by a built-in or external heater, is provided inside a loop formed by the endless fixing belt so as to face the inner circumferential surface of the fixing belt and heat the fixing belt. A pressing roller presses against the outer circumferential surface of the fixing belt at a position corresponding to the location of the metal member inside the loop formed by the fixing belt to form a nip between the fixing belt and the pressing roller through which the recording medium bearing the toner image passes. As the recording medium bearing the toner image passes through the nip, the fixing belt and the pressing roller apply heat and pressure to the recording medium to fix the toner image on the recording medium.
Further, JP-2008-158482-A proposes a fixing device including a stationary member (a first opposing member) against which the pressing roller is pressed via the fixing belt to form a nip and a reinforcement member to reinforce the stationary member.
For example, for a fixing device like that described in JP-2008-158482-A, as the thickness of the metal member is reduced to shorten the warm-up time, the metal member is apt to be thermally deformed during heating. Whether such thermal deformation occurs in a limited area or over a relatively large area of the metal member, it affects the size of a clearance between the fixing belt and the metal member. Consequently, the fixing belt may be unevenly or insufficiently heated, causing uneven or faulty fixing of an output image. In particular, in a case in which the stationary member is pressed against the pressing roller via the fixing belt to form the nip and the metal member is disposed to heat the fixing belt at an area other than the nip, heat of the metal member is easy to disperse at an area close to the nip and difficult to disperse at an area away from the nip. Consequently, the metal member is likely to partially deform, causing a non-negligible failure.